Compose: Incoming email

The Docker image exposes port 25, which is already configured with Zulip’s incoming email server; the Docker Compose configuration defaults to publishing that on port 25.

Determine the publicly-accessible hostname where that port 25 is exposed; in this example, we will use hostname.example.com. This may or may not be the same as SETTING_EXTERNAL_HOST.
Decide what email domain to use for the gateway; for this example, we will use emaildomain.example.com.
Using your DNS provider, create a DNS MX (mail exchange) record configuring email for emaildomain.example.com to be processed by the publicly-accessible hostname of the Docker host publishing port 25. You can check your work using this command:
```
$ dig +short emaildomain.example.com -t MX
1 hostname.example.com
```

Edit compose.override.yaml, and set SETTING_EMAIL_GATEWAY_PATTERN to %s@emaildomain.example.com:

services:
  zulip:
    environment:
      SETTING_EMAIL_GATEWAY_PATTERN: "%s@emaildomain.example.com"

Start the container deployment with docker compose up.

Compose: Incoming email

See also